Method of manufacturing closure flanges

ABSTRACT

A closure flange molded of synthetic plastic resin has an internally threaded cylindrical neck surrounded at one end by a circumferentially enlarged base. An annular groove is formed on the flange base for retention of a thermoplastic bonding element having electromagnetic conducting particles embedded therein. The flange manufacture includes making the bonding element up from an elongated strand into a complete annulus and securely inserting the annular bonding element within the groove in the flange base.

This is a division of application Ser. No. 443,683, filed Feb. 19, 1974,now U.S. Pat. No. 3,873,132.

BACKGROUND OF THE INVENTION

In the manufacture of plastic pails and drums it has been proposed toprovide a closure receiving neck thereon by permanently bonding aninternally threaded closure flange about a flat opening molded withinthe container wall. One advantageously employed bonding techniqueconsists of interposing an electromagnetic bonding element at the flangecontainer wall interface. The bonding element is energized by placingthe closure assembly within a high frequency magnetic field, causing amelt zone and resultant bonding at the flange container wall interface.

Heretofore a number of difficulties presented themselves in attempts torefine the above described bonding technique into an efficient containerfabricating operation. One such difficulty concerns the need for aproduction oriented application of the bonding element to the groove inthe flange base as opposed to a strictly manual operation. Anotherproblem concerns the need for effectively forming a strand ofelectromagnetic bonding material into a complete and continuous annulus.Any space gap created at the intended juncture of the severed strandends may introduce the likelihood of failure in bonding. Once the strandis properly applied to the flange base, the problem arises of securelyretaining the bonding element within the flange base groove duringsubsequent shipping and handling conditions.

SUMMARY

The closure flange assembly and method of manufacture disclosed by theinstant invention advantageously overcomes the above mentioned problemsthrough the formation of a novel groove configuration in the flange basewhich precludes accidental dislodgment of the bonding element under theseverest handling conditions. The method of manufacture herein disclosedincludes feeding the bonding element as an elongated strand into acircular die cavity whereupon closing of the die severs the strand andinserts it as a complete annulus into the flange base groove.

It is, accordingly, a principal object of the invention to provide a newplastic closure assembly for thermoplastic bonding to a plasticcontainer wall opening.

Another object is to provide a method of applying an electromagneticbonding element to a closure flange to facilitate bonding to a containerwall opening through the use of electromagnetic induction.

Still another object is to form an electromagnetic bonding element froman elongated strand into a complete annulus and apply the element to aclosure flange so as to be securely retained thereon.

Other and more detailed objects will in part be obvious and in part bepointed out as the description of the invention taken in conjunctionwith the accompanying drawing proceeds.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a part elevational, part sectional view of the closure flangeof the invention;

FIG. 2 is an enlarged fragmentary sectional view showing the initialposition of the bonding element as it is applied to the flange base;

FIG. 3 is a sectional view similar to FIG. 3 but showing the bondingelement fully seated in the flange base;

FIG. 4 is an enlarged fragmentary top plan view of the flange base withthe bonding element applied;

FIG. 5 is a fragmentary sectional view showing the flange in positionfor bonding within a container wall opening;

FIG. 6 is a sectional view similar to FIG. 4 but showing the completedbond and a closure plug in place;

FIG. 7 is an exploded sectional view of the mechanism for applying thebonding element to the flange base in accordance with the method stepsof the invention;

FIG. 8 is a view taken on line 8--8 of FIG. 7 and looking in thedirection of the arrows;

FIG. 9 is an enlarged fragmentary sectional view similar to FIG. 8showing an advanced position of the strand of bonding material withinthe applying mechanism; and

FIG. 10 is a sectional view similar to FIG. 9 showing a further advancedposition with the strand severed and formed into a complete annulus.

As seen in FIGS. 1-6, the closure flange 1 is molded of a thermoplasticsynthetic resin such as polyethylene and consists of an upstandingcylindrical neck 2 having an interior screw thread 3. The upper end ofthe flange neck has a short unthreaded portion 4 and terminates in acircumferentially enlarged bead 5. The exterior surface of the flangeneck 2 has a short section 6 of reduced diameter beneath the bead 5 andis then circumferentially thickened into a lower pilot portion asindicated at 7. An annular collar 8 surrounds the base of the flangeneck having an upper surface 9. An annular, upwardly opening, groove 10is formed in the upper surface 9 spaced radially outwardly from thethickened pilot portion 7 of the flange neck. The mouth of the groove 10is partially closed off by a pair of annular ribs 11, one at each sideof the groove and extending above the flange upper surface 9. Anadditional annular rib 12, extending above the upper surface 9, isformed at the outer edge of the collar 8.

The final step in the flange manufacture involves the application of anelectromagnetic bonding element 13 to the flange collar for the purposeof forming a thermoplastic bond to a container wall opening. The bondingelement here employed is made up from an elongated strand ofthermoplastic material, circular in cross-section and having minutemetal electromagnetic conducting particles embedded therein. The strandis formed into an annulus having overlapping end surfaces 13a and 13bwhich form a lap joint and insure against the presence of any radial gapin the bonding zone. As clearly see in FIGS. 2 and 3, thecross-sectional diameter of the bonding element 13 is substantiallyequal to the width of the groove 10 and slightly greater than theclosest distance between the ribs 11. A downwardly directed forceapplied to the bonding element 13 causes the flexible ribs 11 to openup, allowing the element to enter the groove 10. Subsequent relaxationof the ribs after the element is fully seated within the groove servesto positively retain the element securely in place. The mechanical gripapplied by the ribs 11 prevents accidental dislodgment of the element 13during packing, shipping and handling of the finished flange.

The bonding of the flange 1 to a plastic container wall section, such asa pail head as indicated at 14, is accomplished by inserting the neck ofthe flange up through the container wall opening 15 which just fits overthe enlarged neck pilot portion 7. In FIG. 5 the undersurface of thecontainer wall, prior to bonding, rests on top of the bonding element 13and just above the ribs 11 and 12. Induction welding of the flange tothe surrounding container wall section commences upon the application ofa vertical force to the assembly and introduction within the magneticfield of a high frequency induction heating generator. As thethermoplastic resin of the element 13 starts to melt, together with thewalls of the groove 10, the ribs 11 and 12 also melt, causing the uppersurface 9 of the collar 8 and the undersurface of the wall 14 to cometogether. The rib 12 being further removed from the bonding element 13tends to melt more slowly, thus forming a dam against the outward flowof bonding material. As seen in FIG. 6, the result is a permanenthomogeneous bonding at the flange container wall interface. It should benoted that the groove and cooperating ribs could also be formed on theundersurface of the flange collar to enable bonding of the flange to theexterior surface of a container wall such as would be required onblow-molded containers.

The bonded flange may then be fitted with a closure plug 16 having athreaded side wall 17 terminating at its upper end in acircumferentially enlarged head 18 designed for gasketing engagementwith the flange bead 5. Further protection against leakage and pilferingcan be had by crimping a tamperproof capseal (not shown) about theflange bead 5.

Considering the method herein disclosed for applying the bonding elementto the flange, attention is directed to FIG. 7 which shows an applyinghead 20 mounted on a vertically moveable shaft 21. The head 20 consistsof an inverted cup-shaped housing 22 having a base wall 23 and adepending cylindrical wall 24 terminating in a lowermost locatingsurface 25. A passage 24a, as clearly seen in FIG. 8, extends angularlythrough the wall 24 so as to communicate with the housing interior. Thebase 23 is formed with a large central opening 26 surrounded by threesmaller holes 27. A cutter 28 is nested within the housing 22 having abase wall 29 surrounded by a depending cylindrical wall 30 terminatingat its lower end in a shearing edge 31. The shaft 21 is slideablyreceived through the center opening 26 in the housing member base 23 andis secured to the cutter base 29 by nut 32. A cylindrical plunger 33 isslideably mounted within the cutter 28 and has an outwardly openinggroove 34 formed in its exterior surface. Three screws 35 extend throughthe holes 27 in the housing base 23 and are secured to the plunger 33. Acoiled compression spring 36 surrounds each of the screws 35 so as toresiliently urge cutter 30 and plunger 33 apart.

In operation a flange 1 is seated on an anvil 37 positioned beneath theapplying head 20. An elongated strand of electromagnetic bondingmaterial 13 is fed into the passage 24a in the housing sidewall 24 and,as seen in FIG. 8, is guided by the groove 34 around the plunger 33 intoan annular form. The head 20 is then lowered down over the flange withthe locating surface 25 resting against the upper surface 9 of theflange collar, and with the plunger 33 resting on top of the flange bead5. Continued downward movement of the shaft 21 overcomes the compressionof springs 36 and urges the cutter 28 downwardly relative to the housingand plunger. In so doing the shearing edge 31 is lowered over thepassage 24a and severs the strand 13 along the interior surface of thehousing wall.

As the my 28 continues to move downwardly, it pushes the element 13ahead of it, forcing the element between the annular upstanding ribs 11on the flange collar. The final downward movement of the cutter 28firmly seats the element 13 within the flange groove 10 whereupon thehead 20 is retracted upwardly and the parts thereof restored to theirinitial position. It should be noted that during the downward urging ofthe element 13 by the cutter 28, the leading cut end 13a and thetrailing cut end 13b are lined up in a common axially extending plane asseen in FIG. 10. As a result the strand of electromagnetic bondingmaterial is formed into a complete uninterrupted annulus with the angledsurfaces 13a and 13b preventing a detrimental radially extending gapfrom occurring at the joint due to minor variations in the strandlength.

From the foregoing it is seen how a container closure flange molded ofsynthetic resin can be very simply assembled with an electromagneticbonding element for thermoplastic induction bonding to a containeropenings. The assembly operation disclosed, while lending itself verywell to an automatic or semiautomatic production operation, alsocontributes to the quality and effectiveness of the bond between theflange and the container wall.

Having described my invention, what I claim is as follows:
 1. A methodof manufacturing closure flanges for electromagnetic bonding tocontainers comprising the steps of molding an annular closure flange ofthermoplastic synthetic resin, supporting said flange in concentricalignment with an applying head, feeding an elongated strand ofelectromagnetic bonding material into said head to form an annulusdisplacing said head and flange toward each other, cutting said strandinto a predetermined length and applying said strand as a completeannulus to said flange as said annulus is discharged from said head. 2.A method of manufacturing closure flanges as in claim 1 and said cuttingof said strand within said head forming a lap joint at the strand ends.3. A method of manufacturing closure flanges as in claim 1 andpositively locking said strand onto said flange.